Significance Neurodegenerative disorders, such as Alzheimer[unreadable]s Disease, effect millions of Americans and cause enormous human suffering and financial burden. We explore the use of neural transplantation to restore damaged brain systems and normal cognitive function. Objectives The present study was carried out to determine whether fetal brain tissue transplanted into the mature hippocampal formation could restore a surgically eliminated cholinergic input. We sought to determine whether transplanted neurons express the phenotypic characteristics of the donor or host brain. Results Tissue from fetal day 45 donors was successfully transplanted into mature macaque monkey brains. After a survival period of 9 months, the histological characteristics and connections of the transplant were assessed. In all cases, there was robust growth and differentiation of the transplanted tissue creating a [unreadable]microbrain[unreadable] in the host hippocampal formation. While cholinergic neurons matured within the transplant and formed connections within the transplant, the cholinergic fibers did not appreciably enter the host brain. Future Directions Future studies will determine whether the administration of growth factors to the host brain might encourage more robust transplant-host interaction. We also plan to carry out similar studies in the entorhinal cortex in which the transplant will be placed in the environment in which it would normally find itself. Since the entorhinal cortex suffers early degeneration in Alzheimer[unreadable]s Disease (AD), these studies may ultimately contribute to restoration in AD patients following diagnosis. KEYWORDS transplantation, recovery of function, neural development